[aprssig] 10 MHz transmitter for APRS

[Stephen H. Smith]

Wes Johnston wrote on 1/12/2005, 8:05 PM:

 > Makes me wonder if PSK31 would be a solution for you....  well the PSK31
 > transmitter kits from http://smallwonderlabs.com/ .  Use one of those
 > with a
 > tinytrack in 300baud mode, and you might have a winner.

The Small Wonder PSK transceivers are very low power devices (5 watts or 
less). PSK31 is effective at very low power levels because: A) It uses 
an extremely narrow bandwidth that intercepts very little noise and QRM, 
and B) not every character has to be received perfectly to understand 
the message.

Standard packet, as used on APRS, requires that EVERY bit of a packet 
burst be received PERFECTLY before ANY data can be recovered from it. 
The 300 baud FSK signal has an effective bandwidth 10s of times wider 
than a PSK signal, and is therefore far more vunerable to noise.

To use HF APRS at all reliably, you will need a decent mobile whip and 
50-100 watts TX output.

I have pondered using an FT-817 with a 5-->100 watt CB amp for this 
application.


Stephen H. Smith                wa8lmf (at) aol.com

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